ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
659 
The thickening and strengthening of the thallus is also an adaptation 
for a saprophytic mode of life. The thallus may be endogenous or 
exogenous ; the latter including the myceliform, corticate, areolate, 
squamose, foliaceous and fruticose thalli ; but there are intermediate 
conditions between the two principal forms. 
The cortex serves as a protection against excessive transpiration, 
and as a storehouse for the characteristic secretions and excretions. It 
is of various forms — pseudo-parenchymatous (the most common), pali- 
sade-like, or fibrous ; or it may consist of only one or two laj^ers of 
hyphoe ; or the whole thallus may consist of a simple mycele in which 
are enclosed a few nests of gonids. The acids, salts, and oily sub- 
stances which the cortex secretes are a protection against the attacks 
of animals. The mode of absorption and disengagement of water in 
the different classes of lichens is described in detail ; in the fruticose 
forms it is absorbed directly from the atmosphere, and not from the 
soil. 
Lichens have a very strong power of respiration, even at very 
low temperatures ; this does not take place, as a rule, over the whole 
extent of the thallus; the portions vhich are especially characterised 
by the power of respiration are the lower portion of the cortex 
and the cyphellte. The gonids are necessarily the organs of assimi- 
lation. 
Function of Lichen-Acids.* — Prof. W. Zopf contests the theory of 
Zukal that the purpose of the acids contained in lichens is their pro- 
tection against the attacks of animals, especially snails. The chief 
enemies of the crustaceous and foliaceous lichens are not snails, but 
much smaller animals, Podurida and Acarina, and to these the lichen 
acids appear to be perfectly innocuous. The author carried out, more- 
over, a series of experiments in feeding snails on slices of potato soaked 
in artificially prepared lichen -acids ; and found that, with the exception 
of vulpinic acid, they were greedily devoured, and appeared to produce 
no injurious results. 
New Coenogonium.f — Dr. H. Gluck finds, in several situations in 
Germany, a new species of this chiefly tropical genus of Discolichenes, 
which he names C. germanicum. The constituent alga is, as in other 
species of the genus, a Trentepohlia, but a new species, T. germanica. 
The lichen occurs on rocks and on the leaves of mosses and liverworts. 
Human Saccharomycosis.t — Prof. F. Curtis has worked out a case 
of Saccharomyces infection, the source of which was a myxomatous 
tumour in the thigh of a young man. From this tumour was isolated 
the Saccharomyces suheutaneus tumefaciens. The parasite exists in two 
forms, the one a free, the other an encapsuled cell. The former is 
peculiar to cultures ; the latter to the living tissues and to old cultures 
in saccharated media. S. subcut. tumefaciens grows well in acid and 
neutral media ; it inverts saccharose, forming ethylic alcohol and acetic 
acid. On beer-wort it has a similar action. It attacks glucose if dissolved 
in yeast-water, but has no action on maltose or lactose. The tumours 
* Biol. Centralbl., xvi. (1896) pp. 593-610. 
t Flora, lxxxii. (1896) pp. 268-85 (1 pi. and 15 figs.). 
X Ann. Inst. Pasteur, x. (1896) pp. 449-68 (2 pis.). 
